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// Copyright 2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "eval/eval/optional_or_step.h"
#include <cstdint>
#include <memory>
#include <utility>
#include "absl/base/optimization.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/types/optional.h"
#include "absl/types/span.h"
#include "common/casting.h"
#include "common/value.h"
#include "eval/eval/attribute_trail.h"
#include "eval/eval/direct_expression_step.h"
#include "eval/eval/evaluator_core.h"
#include "eval/eval/expression_step_base.h"
#include "eval/eval/jump_step.h"
#include "internal/status_macros.h"
#include "runtime/internal/errors.h"
namespace google::api::expr::runtime {
namespace {
using ::cel::As;
using ::cel::ErrorValue;
using ::cel::InstanceOf;
using ::cel::OptionalValue;
using ::cel::UnknownValue;
using ::cel::Value;
using ::cel::runtime_internal::CreateNoMatchingOverloadError;
enum class OptionalOrKind { kOrOptional, kOrValue };
ErrorValue MakeNoOverloadError(OptionalOrKind kind) {
switch (kind) {
case OptionalOrKind::kOrOptional:
return ErrorValue(CreateNoMatchingOverloadError("or"));
case OptionalOrKind::kOrValue:
return ErrorValue(CreateNoMatchingOverloadError("orValue"));
}
ABSL_UNREACHABLE();
}
// Implements short-circuiting for optional.or.
// Expected layout if short-circuiting enabled:
//
// +--------+-----------------------+-------------------------------+
// | idx | Step | Stack After |
// +--------+-----------------------+-------------------------------+
// | 1 |<optional target expr> | OptionalValue |
// +--------+-----------------------+-------------------------------+
// | 2 | Jump to 5 if present | OptionalValue |
// +--------+-----------------------+-------------------------------+
// | 3 | <alternative expr> | OptionalValue, OptionalValue |
// +--------+-----------------------+-------------------------------+
// | 4 | optional.or | OptionalValue |
// +--------+-----------------------+-------------------------------+
// | 5 | <rest> | ... |
// +--------------------------------+-------------------------------+
//
// If implementing the orValue variant, the jump step handles unwrapping (
// getting the result of optional.value())
class OptionalHasValueJumpStep final : public JumpStepBase {
public:
OptionalHasValueJumpStep(int64_t expr_id, OptionalOrKind kind)
: JumpStepBase({}, expr_id), kind_(kind) {}
absl::Status Evaluate(ExecutionFrame* frame) const override {
if (!frame->value_stack().HasEnough(1)) {
return absl::Status(absl::StatusCode::kInternal, "Value stack underflow");
}
const auto& value = frame->value_stack().Peek();
auto optional_value = As<OptionalValue>(value);
// We jump if the receiver is `optional_type` which has a value or the
// receiver is an error/unknown. Unlike `_||_` we are not commutative. If
// we run into an error/unknown, we skip the `else` branch.
const bool should_jump =
(optional_value.has_value() && optional_value->HasValue()) ||
(!optional_value.has_value() && (cel::InstanceOf<ErrorValue>(value) ||
cel::InstanceOf<UnknownValue>(value)));
if (should_jump) {
if (kind_ == OptionalOrKind::kOrValue && optional_value.has_value()) {
frame->value_stack().PopAndPush(optional_value->Value());
}
return Jump(frame);
}
return absl::OkStatus();
}
private:
const OptionalOrKind kind_;
};
class OptionalOrStep : public ExpressionStepBase {
public:
explicit OptionalOrStep(int64_t expr_id, OptionalOrKind kind)
: ExpressionStepBase(expr_id), kind_(kind) {}
absl::Status Evaluate(ExecutionFrame* frame) const override;
private:
const OptionalOrKind kind_;
};
// Shared implementation for optional or.
//
// If return value is Ok, the result is assigned to the result reference
// argument.
absl::Status EvalOptionalOr(OptionalOrKind kind, const Value& lhs,
const Value& rhs, const AttributeTrail& lhs_attr,
const AttributeTrail& rhs_attr, Value& result,
AttributeTrail& result_attr) {
if (InstanceOf<ErrorValue>(lhs) || InstanceOf<UnknownValue>(lhs)) {
result = lhs;
result_attr = lhs_attr;
return absl::OkStatus();
}
auto lhs_optional_value = As<OptionalValue>(lhs);
if (!lhs_optional_value.has_value()) {
result = MakeNoOverloadError(kind);
result_attr = AttributeTrail();
return absl::OkStatus();
}
if (lhs_optional_value->HasValue()) {
if (kind == OptionalOrKind::kOrValue) {
result = lhs_optional_value->Value();
} else {
result = lhs;
}
result_attr = lhs_attr;
return absl::OkStatus();
}
if (kind == OptionalOrKind::kOrOptional && !InstanceOf<ErrorValue>(rhs) &&
!InstanceOf<UnknownValue>(rhs) && !InstanceOf<OptionalValue>(rhs)) {
result = MakeNoOverloadError(kind);
result_attr = AttributeTrail();
return absl::OkStatus();
}
result = rhs;
result_attr = rhs_attr;
return absl::OkStatus();
}
absl::Status OptionalOrStep::Evaluate(ExecutionFrame* frame) const {
if (!frame->value_stack().HasEnough(2)) {
return absl::InternalError("Value stack underflow");
}
absl::Span<const Value> args = frame->value_stack().GetSpan(2);
absl::Span<const AttributeTrail> args_attr =
frame->value_stack().GetAttributeSpan(2);
Value result;
AttributeTrail result_attr;
CEL_RETURN_IF_ERROR(EvalOptionalOr(kind_, args[0], args[1], args_attr[0],
args_attr[1], result, result_attr));
frame->value_stack().PopAndPush(2, std::move(result), std::move(result_attr));
return absl::OkStatus();
}
class ExhaustiveDirectOptionalOrStep : public DirectExpressionStep {
public:
ExhaustiveDirectOptionalOrStep(
int64_t expr_id, std::unique_ptr<DirectExpressionStep> optional,
std::unique_ptr<DirectExpressionStep> alternative, OptionalOrKind kind)
: DirectExpressionStep(expr_id),
kind_(kind),
optional_(std::move(optional)),
alternative_(std::move(alternative)) {}
absl::Status Evaluate(ExecutionFrameBase& frame, Value& result,
AttributeTrail& attribute) const override;
private:
OptionalOrKind kind_;
std::unique_ptr<DirectExpressionStep> optional_;
std::unique_ptr<DirectExpressionStep> alternative_;
};
absl::Status ExhaustiveDirectOptionalOrStep::Evaluate(
ExecutionFrameBase& frame, Value& result, AttributeTrail& attribute) const {
CEL_RETURN_IF_ERROR(optional_->Evaluate(frame, result, attribute));
Value rhs;
AttributeTrail rhs_attr;
CEL_RETURN_IF_ERROR(alternative_->Evaluate(frame, rhs, rhs_attr));
CEL_RETURN_IF_ERROR(EvalOptionalOr(kind_, result, rhs, attribute, rhs_attr,
result, attribute));
return absl::OkStatus();
}
class DirectOptionalOrStep : public DirectExpressionStep {
public:
DirectOptionalOrStep(int64_t expr_id,
std::unique_ptr<DirectExpressionStep> optional,
std::unique_ptr<DirectExpressionStep> alternative,
OptionalOrKind kind)
: DirectExpressionStep(expr_id),
kind_(kind),
optional_(std::move(optional)),
alternative_(std::move(alternative)) {}
absl::Status Evaluate(ExecutionFrameBase& frame, Value& result,
AttributeTrail& attribute) const override;
private:
OptionalOrKind kind_;
std::unique_ptr<DirectExpressionStep> optional_;
std::unique_ptr<DirectExpressionStep> alternative_;
};
absl::Status DirectOptionalOrStep::Evaluate(ExecutionFrameBase& frame,
Value& result,
AttributeTrail& attribute) const {
CEL_RETURN_IF_ERROR(optional_->Evaluate(frame, result, attribute));
if (InstanceOf<UnknownValue>(result) || InstanceOf<ErrorValue>(result)) {
// Forward the lhs error instead of attempting to evaluate the alternative
// (unlike CEL's commutative logic operators).
return absl::OkStatus();
}
auto optional_value = As<OptionalValue>(static_cast<const Value&>(result));
if (!optional_value.has_value()) {
result = MakeNoOverloadError(kind_);
return absl::OkStatus();
}
if (optional_value->HasValue()) {
if (kind_ == OptionalOrKind::kOrValue) {
result = optional_value->Value();
}
return absl::OkStatus();
}
CEL_RETURN_IF_ERROR(alternative_->Evaluate(frame, result, attribute));
// If optional.or check that rhs is an optional.
//
// Otherwise, we don't know what type to expect so can't check anything.
if (kind_ == OptionalOrKind::kOrOptional) {
if (!InstanceOf<OptionalValue>(result) && !InstanceOf<ErrorValue>(result) &&
!InstanceOf<UnknownValue>(result)) {
result = MakeNoOverloadError(kind_);
}
}
return absl::OkStatus();
}
} // namespace
std::unique_ptr<JumpStepBase> CreateOptionalHasValueJumpStep(bool or_value,
int64_t expr_id) {
return std::make_unique<OptionalHasValueJumpStep>(
expr_id,
or_value ? OptionalOrKind::kOrValue : OptionalOrKind::kOrOptional);
}
std::unique_ptr<ExpressionStep> CreateOptionalOrStep(bool is_or_value,
int64_t expr_id) {
return std::make_unique<OptionalOrStep>(
expr_id,
is_or_value ? OptionalOrKind::kOrValue : OptionalOrKind::kOrOptional);
}
std::unique_ptr<DirectExpressionStep> CreateDirectOptionalOrStep(
int64_t expr_id, std::unique_ptr<DirectExpressionStep> optional,
std::unique_ptr<DirectExpressionStep> alternative, bool is_or_value,
bool short_circuiting) {
auto kind =
is_or_value ? OptionalOrKind::kOrValue : OptionalOrKind::kOrOptional;
if (short_circuiting) {
return std::make_unique<DirectOptionalOrStep>(expr_id, std::move(optional),
std::move(alternative), kind);
} else {
return std::make_unique<ExhaustiveDirectOptionalOrStep>(
expr_id, std::move(optional), std::move(alternative), kind);
}
}
} // namespace google::api::expr::runtime